In current industrial practice, known silicocalcareous masses are produced from an intimate mixture of lime, ground or fossil silica and asbestos suspended in water. The paste thus obtained, introduced into containers, of the bottle type, is then subjected to the action of steam in an autoclave to initiate and completely perform the lime-silica reaction which gives rise to the silicocalcareous mass; then it is transferred into a drying furnace to eliminate the water and create the desired porosity.
Asbestos is added to the aqueous composition of silica and lime for its action of reinforcing fiber and suspending agent. Now, recent constraints relating to health and safety conditions linked to the handling of asbestos have led to reconsidering the use of this natural fiber whose characteristic properties, in the production of porous silicocalcareous masses, are to strengthen the crystalline structure and to cooperate in maintaining the suspension of solid products: silica and lime in a large amount of water.
It is known that the stabilization of the paste before cooking can be notably improved by the use of suspending agents. From French Pat. No. 1 358 446 it is known of to add substantial amounts up to 10% of organic agents for putting the paste materials into suspension. Some cellulose derivatives, such as alkyl hydroxyalkyl celluloses, in particular methyl and ethyl hydroxyethyl celluloses, make it possible to obtain an excellent stabilization of the suspension containing asbestos.
Consideration has been given to compensating for the elimination of asbestos by the addition of suspending agents in large amounts. Now, it was found that if the addition of an organic suspending agent in large amount can notably correct the decanting defect of solid products during production of the silica/lime paste and water, because of the destruction of this type of organic compound during cooking of the paste, a lowering of the mechanical properties of the high-porosity silicocalcareous masses was noted. The fragility and friability of the porous materials thus obtained are such that they are unsuitable for the application in question.
Further, European Pat. No. 0064 916 teaches that the addition of amorphous ultrafine synthetic silica with a large specific surface of 150 to 300 m.sup.2 per gram of high absorption capacity, as total or partial replacement of the ground silica, makes it possible to obtain homogeneous silicocalcareous masses with a porosity on the order of 90% and exhibiting a crushing strength of 1.5 to 2 MPa. However, the large amount of amorphous ultrafine synthetic silica, representing 70 to 100% by weight of the total silica, causes a certain difficulty in working up the paste and leads to a high cost in obtaining silicocalcareous masses on an industrial scale.
In the field of thermal insulation with cement type materials, the use of various reinforcing fibers, of organic or mineral origin, has been considered.
Thus, U.S. Pat. No. 4 128 434 specifies the use of wood fibers, polyester, cotton or the like, replacing asbestos, in working up of high-density thermal insulating material in the form of molded slabs or panels.
The use of cellulose fibers was considered in U.S. Pat. No. 4 238 240, also in the sector of thermal insulations, obtained by compacting of a paste previously subjected to a cooking toward 800.degree. C.
U.S. Pat. No. 3 895 096 proposes using cellulose fibers and alkaline-resistant glass fibers in the production of a very porous, very light, slightly resistant material.
The qualities required for a good thermal insulation are different from those required for a mass intended for storing of dissolved gas. The silicocalcareous mass is to be formed directly inside the bottle under such conditions that it is monolithic, homogeneous and fills the cylinder and head of the bottle without lacunas. After cooking in an autoclave, then drying, the bottle of acetylene, filled with silicocalcareous mass, is ready to use.
Further, the porous masses used in filling the bottles should meet the requirements of solidity. For, the porous mass contained in the bottles of gas is subjected to impacts and vibrations during shipment and handling of the bottles. Further, the mass should resist the stresses of successive emptyings and fillings with gas and of the possible solvent of this gas.
On the other hand, an excellent thermal insulation should have the slightest possible density while having a relatively low mechanical strength.
All the techniques proposed for obtaining thermal insulating materials, which do not take into account decanting or seperation of the paste, and therefore also do not take into account the homogeneity of the final material and direct obtaining in the container of the finished material ready to use, are not suited for the production of homogeneous porous silicocalcareous mass for storing of gas and in particular of acetylene and its solvent.
On the other hand, U.S. Pat. No. 4 349 463 refers to the use of alkaline-resistant glass fibers in the production of masses for storage of acetylene. These very special, expensive fibers lead to the production of a costly industrial product for storing acetylene.